egs_alias_table.h

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/*
###############################################################################
#
#  EGSnrc egs++ alias table headers
#  Copyright (C) 2015 National Research Council Canada
#
#  This file is part of EGSnrc.
#
#  EGSnrc is free software: you can redistribute it and/or modify it under
#  the terms of the GNU Affero General Public License as published by the
#  Free Software Foundation, either version 3 of the License, or (at your
#  option) any later version.
#
#  EGSnrc is distributed in the hope that it will be useful, but WITHOUT ANY
#  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
#  FOR A PARTICULAR PURPOSE.  See the GNU Affero General Public License for
#  more details.
#
#  You should have received a copy of the GNU Affero General Public License
#  along with EGSnrc. If not, see <http://www.gnu.org/licenses/>.
#
###############################################################################
#
#  Author:          Iwan Kawrakow, 2005
#
#  Contributors:    Ernesto Mainegra-Hing
#                   Marc Chamberland
#
###############################################################################
*/
 
 
#ifndef EGS_ALIAS_TABLE_
#define EGS_ALIAS_TABLE_
 
#include "egs_libconfig.h"
#include "egs_rndm.h"
#include <vector>
 
typedef EGS_Float(*EGS_AtFunction)(EGS_Float,void *);
 
class EGS_EXPORT EGS_AliasTable {
 
public:
 
    EGS_AliasTable() : n(0) {};
 
    EGS_AliasTable(const EGS_AliasTable &t) : n(0) {
        copy(t);
    };
 
    EGS_AliasTable(int N, const EGS_Float *x, const EGS_Float *f,
                   int Type = 1) : n(0) {
        initialize(N,x,f,Type);
    };
 
 
    EGS_AliasTable(EGS_Float xmin, EGS_Float xmax, EGS_Float accu, int nmax,
                   EGS_AtFunction func, void *data) : n(0) {
        initialize(xmin,xmax,accu,nmax,func,data);
    };
 
    void initialize(int N, const EGS_Float *x, const EGS_Float *f,
                    int Type = 1);
 
    int initialize(EGS_Float xmin, EGS_Float xmax, EGS_Float accu, int nmax,
                   EGS_AtFunction func, void *data);
 
    EGS_Float sample(EGS_RandomGenerator *rndm) const;
 
    int sampleBin(EGS_RandomGenerator *rndm) const;
 
    EGS_Float getAverage() const {
        return average;
    };
 
    EGS_Float getMaximum() const {
        return xi[n-1];
    };
 
private:
 
    int       n;     
    int       np;    
    EGS_Float *fi;   
    EGS_Float *xi;   
    EGS_Float *wi;   
    EGS_Float average;
    int       *bin;  
    int       type;  
    void      copy(const EGS_AliasTable &t);
    void      clear();
    void      allocate(int N, int Type);
    void      make();
 
 
};
 
class EGS_EXPORT EGS_SimpleAliasTable {
 
public:
 
    EGS_SimpleAliasTable(int N, const EGS_Float *f);
 
    ~EGS_SimpleAliasTable();
 
    int sample(EGS_RandomGenerator *rndm) const {
        int bin = (int)(rndm->getUniform()*n);
        return rndm->getUniform() < wi[bin] ? bin : bins[bin];
    };
 
private:
 
    int       n;          
    EGS_Float *wi;        
    int       *bins;      
 
};
 
 
#endif